(what i would really like to get rid of on my body is the little pouch of fat on my lower abdomen. and i know that will take mostly diet. i already do about 70 situps a day.)
If doing 70 situps a day is not advancing you towards your goal then try something else. To keep doing the same thing and expecting different results is a little shortsighted!
You are corect that diet is the major factor in body fat reduction, however there are a couple of problems with your "i already do about 70 situps a day" statement:
1. abs are like any other muscle and should be rested 48 hours between exercise sessions for best results.
2. high intensity often produces better results than high volume. Try some other variations that only allow you to do 12-15 repetitions per set, and you only need 2-3 sets (24-45 total repetitions). Variations could be: incline situps, weighted situps, bicycles, etc.
3. try other movements, like leg raises, hanging leg raises, heavy deadlifts, good mornings, squats, etc.
4. and, of course, in general, you can't spot reduce, so you will have to reduce your overall body fat level to see results in any place.